Synthesis and physico-chemical properties of semiconducting ZnCr2Se4-policrystals doped with dysprosium
Barsova Z., Jendrzejewska I.
Химия и современные технологии
The compound ZnCr2Se4 crystallizes in cubic spinel structure and is a semiconductor with helical magnetic structure below the Néel temperature TN = 20 K with a strong ferromagnetic (FM) component confirmed by a large positive Curie-Weiss temperature (q) of 115 K. It is known that elements substitution can strongly influence on parent compound properties. In our research we used dysprosium as a dopant.
The compounds based on the system Zn1-xDyxCr2Se4 were synthesized by ceramic method, according to the following reactions:
(1 − x)ZnSe + xDySe + Cr2Se3 = Zn1−xDyxCr2Se4, x = 0.05÷0.1
ZnSe + (1 − x)Cr2Se3 + xDy2Se3 = ZnCr2−xDyxSe4, x = 0.05÷0.1
XRD and Rietveld refinement analysis were used in order to obtain structural parameters. Chemical composition defined using JEOL scanning microscope (SE 6480). The results showed less Dy content then it was expected. The structural parameters increase with increasing of Dy amount. The results of XRD analysis showed only one spinel phase.
Fig.1 The polycrystalline compounds obtained in the ZnCr2Se4:Dy system: Zn0.98Cr1.68Dy0.06Se4 (left side), Zn0.92Dy0.06Cr2.01Se4 (right side)
The magnetic isotherms of the obtained compounds were studied using high magnetic stationary fields (up to 14T). It was confirmed increasing of magnetization with increasing of Dy ions, in tetrahedral and octahedral positions, respectively.
Decreasing of paramagnetic Curie-Wiess temperature with increasing of Dy amount indicates the boost of the antiferromagnetic interactions.
The results of XANES and EXAFS showed that Dy3+ ions are located in the same chemical environment.